Benign prostatic hyperplasia (BPH) or “enlarged prostate” refers to the non-cancerous (benign) growth of the prostate gland. While BPH is the most common prostate problem in men over 50 years of age, the growth of the prostate begins with microscopic nodules around 25 years of age but rarely produces symptoms before the age of 40. It is estimated that 6.3 million men in the United States alone suffer from BPH. The disease is responsible for 6.4 million doctor visits and more than 400,000 hospitalizations per year.
The exact cause of BPH is unknown but it is generally thought to involve hormonal changes associated with the aging process. Testosterone likely plays a role in BPH as it is continually produced throughout a man's lifetime and is a precursor to dihydrotestosterone (DHT) which induces rapid growth of the prostate gland during puberty and early adulthood. When fully developed, the prostate gland is approximately the size of a walnut and remains at this size until a man reaches his mid-forties. At this point the prostate begins a second period of growth which for many men often leads to BPH later in life.
In contrast to the overall enlargement of the gland during early adulthood, benign prostate growth occurs only in the central area of the gland called the transition zone, which wraps around the urethra. As this area of the prostate grows, the gland presses against the urethra and causes a number of lower urinary tract symptoms (LUTS) such as difficult urination (obstructive symptoms) and painful urination (storage symptoms). Eventually, the bladder itself weakens and loses the ability to empty itself.
Obstructive symptoms such as intermittent flow or hesitancy before urinating can severely reduce the volume of urine being eliminated from the body. If left untreated, acute urine retention can lead to other serious complications such as bladder stones, urinary tract infections, incontinence, and, in rare cases, bladder damage and/or kidney damage. These complications are more prevalent in older men who are also taking anti-arrhythmic drugs or anti-hypertensive (non-diuretic) medications. In addition to the physical problems associated with BPH, many men also experience anxiety and a reduced quality of life.
Initial symptoms of BPH are most often treated with medication such as alpha-blockers and anti-androgens. Men suffering with moderate to severe BPH symptoms typically must undergo surgery. Transurethral resection of the prostate (TURP) is the standard surgical procedure, which however may lead to a number of complications:                Bleeding or secondary hemorrhage                    The shallow penetration of the tissue in combination with the resection of large volumes leads to an opening of many vessels, which subsequently bleed into the cavity of the surgery. In approximately 1% of cases this leads to severe hemorrhages. with the result that even a blood transfusion may be required. Sometimes, due to a secondary hemorrhage, a surgical hemostasis with another narcosis may become necessary. In all cases continuous flushing is required to ensure free visibility. Moreover, patients remain in hospital under postoperative supervision for 5-7 days to enable an adequate response in cases of secondary hemorrhages. Even coughing can cause such hemorrhages.                        “TURP-syndrome”                    Within the resectoscope there is a wire loop fed by an electric current. This wire removes layers of diseased tissue in the bladder or prostate while hemorrhages are cauterized through electricity. The physical principle corresponds to the one employed in RF-surgery. Throughout the operation, irrigation liquid is continuously introduced via the resectoscope, serving the filling of the bladder on one hand and the excretion of resected tissue and blood on the other. This solution is hypotensive, i.e. it has a lower concentration of electrolytes than the blood. The low electrolyte concentration is necessary to ensure a low conductivity. Through the flushing of water into open blood vessels the salt and water balance can be disturbed (“infiltration”). The result is cardiac and circulatory stress, which may lead to acute right-sided heart failure. These may even end fatally. Symptoms are nausea, vomiting, confusion and restlessness.                        Incontinence, i.e. the inability to retain urine deliberately.                    The frequency can vary greatly. The complication is rare with an experienced surgeon (approx. 1%). On the other hand an incontinence caused by BPH can improve after the operation.                        Impotence                    Here the incidents also vary considerably (10-15%). One possible cause is the damage to nerves at the outer side of the prostate capsule through electricity; psychological factors are also being discussed. Overall only a small number of patients are affected. Studies regarding impotence and BPH indicate that impotence occurred with a variety of treatments (including waiting).                        Cystitis and epididymitis occur frequently but respond well to antibiotic treatment.        Discharge of seminal fluid into the bladder (60-80%).        Perforation of prostate capsule or rectum.        
Potential long-term consequences are:                Erectile dysfunction.        Retrograde ejaculation (no emission of semen).        Months or years after the treatment a stricture of the urethra through scarring as well as a narrowing of the bladder neck may occur. A renewed formation of adenoma is also possible.        
However, a number of other, less invasive methods are nowadays available:
transurethral incision of the prostate (TUIP), transurethral microwave thermotherapy (TUMT), transurethral electro vaporization (TUVP), transurethral needle ablation (TUNA), and laser surgery of the prostate gland.
In the TUMT, the target tissue is heated through a microwave probe. Since only sedation is required, this treatment suggests itself in cases where the narcosis would present a high risk for the patient. The treatment is however only possible where the prostate has a small volume. Contraindications for the TUMT are pacemakers or metals in osteosynthetic materials.
A TUNA is also performed under local anesthesia, which means that the treatment can also be applied in high risk patients. However, it is only appropriate tfor a prostate volume of <60 ml. There are no reliable data at present about the effectiveness of the treatment. In up to 14% of cases a renewed operation is required.
In the adenoma enucleation (removal of prostate tissue through surgical incision) large volumes of prostate tissue of more than 75 ml can be removed. An indication for this operation can also be a symptomatic diverticulum of the bladder (outwards protuberance of the bladder wall) or a large bladder stone. It is an advantage that the outlet of the bladder is in direct visibility for the surgeon, so that injuries to the bladder can certainly be avoided. The adenoma can be removed completely. The complications of a TURP-syndrome do not occur. As with all ‘open operations’ this procedure however requires longer hospitalization.
Nowadays the above mentioned urological indications can be treated alternatively by means of laser radiation. In comparison with the “classical” forms of treatment these procedures have the advantage of superior hemostasis (arrest of bleeding) and minimal invasive surgery.
Various systems are currently employed for the therapy with laser radiation through solid-state lasers, such as diode-pumped solid-state lasers (DPSSL) or frequency doubled DPSSL. In these treatments light is generated through flashlights or laser diodes, which in turn is used for the stimulation of the solid-state laser. A few examples of such systems and the applied solid-state lasers are described in the following.
The so-called KTP laser (potassium-titanyl-phosphate laser), which is a frequency doubled solid-state laser with a wavelength of 532 nm, has primarily an ablative effect, which means that the target tissue is vaporized. Typical laser parameters are pulse durations of a few micro- to milliseconds as well as applications in continuous operation (continuous wave, cw) with a medium power of about 80 W. An advantage of this form of therapy is that the patient requires a bladder catheter only briefly, i.e. for 1 to 2 days. Disadvantages are the high costs for laser and application system based on glass fiber. Moreover, there is a danger of perforation of the bladder wall, with potential lethal consequences if the glass fibers should break.
The Nd:YAG-Laser (neodymium-doped yttrium aluminum garnet laser) emits light with a wavelength of 1064 nm, having a secondary ablative (coagulating) effect, and causing necrosis in the tissue, which desquamates within four weeks. During this time the patient has to tolerate a bladder catheter, i.e. the healing process is prolonged and the patient does not experience an immediate alleviation of his ailments. Typical parameters of treatment are pulse durations of a few micro- to a few milliseconds and cw-applications with a medium power of about 80 W.
Interstitial laser coagulation, in other words, coagulation within the tissue leads to a reduction of the adenoma volume through atrophy and scarring. Since no tissue is removed there is no immediate alleviation. The treatment is minimal invasive but causes higher costs.
All these systems have one disadvantage in common, which is the fact that they principally require a light source in addition to the solid-state laser, yielding to a relatively inefficient conversion of electric power to optical power (“wall plug efficiency”). The described lasers are mostly equipped with a three-phase connection and frequently need water cooling. Even up-to-date systems, operating on one phase only, require a fuse protection of up to 32 A. This requires special installations for a corresponding electrical power supply to operate these systems, which prevents the mobile application of these systems. The heaviness of such systems, weighing about 140 kg or more, in addition to the requirements of a cooling medium, makes a mobile application prohibitive, too.
Furthermore, the complex configuration of such systems, especially the use of consumables such as flash lamps or of cooling systems with liquid cooling agents, requires regular and sometimes costly maintenance, which is also a disadvantage.